I’ve replaced the main sail furling line recently on my Dufour 455. Your furling system appears to be a Sparcraft in mast furler, which is identical to ours. I simply followed the instructions in the Sparcraft document attached.
Also attached photos of rigging of the mast foot wrt main sail furling lines. The green & white line is the outhaul coming off the mast end of the boom to turning block stbd side mast foot, the grey & red line is the furling line to turning block pt side mast foot via turning block at boom end of vang and the black line in 3528 is the vang line to turning block pt side mast step.
Hope this helps.